fix(datetime): clamp date between min and max when using month picker (#27185)

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

When using the dropdown month picker, the value is updated when the
month is changed, to follow native behavior. However, because only the
month is updated (the day remains the same), it's possible for the newly
chosen date to fall outside the min/max bounds of the datetime.

For example, if you have a datetime with `min="2021-01-15"
value="2021-02-01"`, then use the month picker to switch to January, the
new value will be `2021-01-01` which is earlier than the `min`.

<!-- Issues are required for both bug fixes and features. -->
Issue URL: Resolves #27027


## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

When updating the `activeParts` in any scenario, the date to set is now
clamped between the max and min.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

core/src/components/datetime/test/minmax/datetime.e2e.ts

@@ -240,6 +240,7 @@ test.describe('datetime: minmax', () => {
       skip.rtl();
       skip.mode('ios', 'This implementation is the same across modes.');
     });
+
     test('should reset to min time if out of bounds', async ({ page }) => {
       await page.setContent(`
         <ion-datetime
@@ -259,6 +260,7 @@ test.describe('datetime: minmax', () => {
 
       await expect(datetime).toHaveJSProperty('value', '2022-10-10T08:00:00');
     });
+
     test('should reset to max time if out of bounds', async ({ page }) => {
       await page.setContent(`
         <ion-datetime
@@ -278,6 +280,28 @@ test.describe('datetime: minmax', () => {
 
       await expect(datetime).toHaveJSProperty('value', '2022-10-10T08:00:00');
     });
+
+    test('should adjust to in-bounds when using month picker', async ({ page }) => {
+      await page.setContent(`
+        <ion-datetime
+          min="2022-01-15"
+          value="2022-02-01"
+          presentation="date"
+        ></ion-datetime>
+      `);
+
+      const datetime = page.locator('ion-datetime');
+      const monthYearToggle = page.locator('ion-datetime .calendar-month-year');
+      const monthColumnItems = page.locator('ion-datetime .month-column .picker-item:not(.picker-item-empty)');
+
+      await monthYearToggle.click();
+      await page.waitForChanges();
+
+      await monthColumnItems.nth(0).click(); // switch to January
+      await page.waitForChanges();
+
+      await expect(datetime).toHaveJSProperty('value', '2022-01-15T00:00:00');
+    });
   });
 
   test.describe('datetime: confirm button', () => {

core/src/components/datetime/utils/manipulation.ts

@@ -2,7 +2,7 @@ import type { DatetimeParts } from '../datetime-interface';
 
 import { isSameDay } from './comparison';
 import { getNumDaysInMonth } from './helpers';
-import { parseAmPm } from './parse';
+import { clampDate, parseAmPm } from './parse';
 
 const twoDigit = (val: number | undefined): string => {
   return ('0' + (val !== undefined ? Math.abs(val) : '0')).slice(-2);
@@ -333,7 +333,8 @@ export const calculateHourFromAMPM = (currentParts: DatetimeParts, newAMPM: 'am'
 /**
  * Updates parts to ensure that month and day
  * values are valid. For days that do not exist,
- * the closest valid day is used.
+ * or are outside the min/max bounds, the closest
+ * valid day is used.
  */
 export const validateParts = (
   parts: DatetimeParts,
@@ -341,7 +342,7 @@ export const validateParts = (
   maxParts?: DatetimeParts
 ): DatetimeParts => {
   const { month, day, year } = parts;
-  const partsCopy = { ...parts };
+  const partsCopy = clampDate({ ...parts }, minParts, maxParts);
 
   const numDays = getNumDaysInMonth(month, year);